Device for heat treatment by way of forced gas convection, forming a bakery, pastry, pork-butchery oven or the like

ABSTRACT

A device for heat treatment comprising a muffle, heating means, a fan and a treatment chamber limited on one of its sides by an inner wall of the muffle, the cross-sections of said chamber having the shape of trapezia, the larger base of which is located on the fan side of the device. The heating means are constituted by at least one gas burner. The device comprises a casing forming a heat exchanging element surrounding said heating means and being placed within the hot gases circulating in the muffle.

[451 March 6, 1973 United States Patent 91 Pere 3,324,844 6/1967Huffman............................ 126/21A 3,384,068 5/1968 3,605,7179/1971 Sauer...............,..................126/2l A Perry et al.

[ DEVICE FOR HEAT TREATMENT BY WAY OF FORCED GAS CONVECTION,

FOREIGN PATENTS OR APPLICATIONS Francois Caillarec Pere, Quimper,1,124,382 6/1956 France................................126/21 A France[73] Assignee: Capic-Etablissements Caillarec, Primary Examiner-CharlesMyhre Quimper, France Attorney-Stemberg & Blake Feb. 1, 1971 [21] Appl.No.: 111,241

ABSTRACT [22] Filed:

A device for heat treatment comprising a muffle, heating means, a fanand a treatment chamber limited on one of its sides by an inner wall ofthe muffle, the cross-sections of said chamber having the shape oftrapezia, the larger base of which is located on the fanFrance.................... ............7003575 side of the device. Theheating means are constituted by at least one gas burner. The devicecomprises a casing forming a heat exchanging element surrounding saidheating means and being placed within the hot gases circulating in themuffle.

Afi R 1/ 3 2 7 /1 6 24R6 429 C1 mR m IA mi 2 ""6 "2 "1 Th "C r. "0 Us LI0 W d td I Q- UmF 111111 2 8 555 [rlrl 7 Claims, 5 Drawing Figures [56]References Cited UNITED STATES PATENTS 3,148,674 9/1964 Boardman et a1.....,............l26/2l A PATENTED 61975 3.719.180

SHEET EEF 2 DEVICE FOR I-IEAT TREATMENT BY WAY OF FORCED GAS CONVECTION,FORMING A BAKERY, PASTRY, PORK-BUTCHERY OVEN OR THE LIKE The presentinvention has for its object a device for heat treatment of foodproducts, of the forced gas convection type, adapted to be used, inparticular, as a bakery, pastry, pork-butchery oven or the like, forbaking, pre-heating, or heating food products.

The few devices for heat treatment of food products by way of forced gasconvection, wherein use was made of gas burners located within the verymuffle of the device, had the following drawbacks a considerable part ofthe sensible heat of the burnt gases was lost as a result ofinsufficient heat exchange through the walls of the sealed sheathcontaining the burners and of the relatively direct escape of the burntgases in the chimney or chimneys the arrangements which were resortedto, although relatively efficient from the heating point of view, led toa lack of sufficient available space in some portions of the muffle, sothat it was not possible to use removable trolleys carrying thefoodstuffs and, therefore, the baking rates were reduced the saiddevices were not provided with the system of circulation which is wellknown at the present time and particularly efficient, according to whichthe hot gases proceeding from the medial region of the chamber of thetreatment device were sucked by a fan placed in a medial plane of themuffle and delivered symmetrically towards the side walls of the saidchamber and then along the said wall, to be thereafter recycled in themedial region of the oven.

The heat treatment device according to the present invention enables thevarious aforesaid drawbacks to be remedied.

The heat treatment device according to the invention pertains to thegeneral type described above and is characterized in that the heatingmeans are constituted by at least one gas burner of the barortube-type,or of the single-jet type, the latter being protected from theair flows produced in the oven chamber by a casing or enclosure whichsurrounds it at least on a portion of its periphery, the said casing orenclosure being located within the hot gases circulating in the muffle,so as to constitute a heat exchanging and distributing element.

According to a preferred form of embodiment of the present invention,the said fan is secured to the rear wall of the muffle, and the saidcasing is constituted by two substantially parallel and vertical metalsheets perpendicular to the fan shaft and located on either side of thesaid burner which is preferably constituted by a horizontal gas bar ortube, the said sheets being located in front of the fan and their sideedges being bent towards the front and joined together, whereas apassageway is provided transversely of and through the said sheets inconfronting relationship to the said fan,

so as'to allow the passage of the hot gases proceeding 6 from theinterior of the chamber towards the space provided within the saidcasing and the rear wall of the oven, the said bent edges being locatedat a certain distance from the side walls of the muffle so as to allowthe passage of the hot gases proceeding from the space provided betweenthe said casing and the rear wall of the muffle towards the interior ofthe chamber.

According to another preferred form of embodiment of the invention, thedevice comprises two casings of the aforesaid type, placed symmetricallywith respect to the said medial plane, within the treatment chamberproper, in immediate proximity to the muffle walls, so that the saidcasing is licked on one side by the gas flow entering the said chamberand on the other side by the gas flow passing through the said casingtowards the said fan.

The invention will be better understood and other objects,characteristics and advantages thereof will appear as the followingdescription proceeds, with reference to the appended drawings givensolely by way of example illustrating two forms of embodiment of theinvention and wherein FIG. 1 is a horizontal sectional view of a heattreat- 7 ment device according to a first form of embodiment of thepresent invention FIG. 2 is a vertical sectional view upon the lineII-II of FIG. 1 of the same device FIG. 3 is a perspective view of therear metal sheet of the casing of the heat treatment device of FIG. 1

FIG. 4 is a vertical sectional view, in parallel relationship to theinlet door, of a heat treatment device according to a second form ofembodiment of the invention FIG. 5 is a longitudinal sectional view uponthe line VV of FIG. 4 of the said device.

Referring now to FIGS. 1 to 3, the heat treatment device comprises amuffle 1, made for instance from a refractory or heat insulatingmaterial, two fans 2 and 3 secured to the rear wall 1c of the muffle, agas tube burner 4, a casing 5 for the latter and a trolley 6 for movingin or out the products to be treated, the said muffle being closed bymeans of a door 1a.

The gas tube burner 4 is fed through a gas (town gas, butane or propane)intake piping, not shown for the sake of clarity the gas tube burner isarranged on the sole or bed lb of the oven and is fed with air suppliedfrom the exterior through two ducts 7 (portions 7a and 7b) and 8(portions 8a and 8b) opening into the casing 5.

The treatment chamber 9 is constituted by the portion in front of thecasing 5, i.e., the space comprised between the said casing and the doorIn the treatment chamber 9 is intended to contain the products to betreated which may be arranged on a system of removable or stationarytrays or plates connected to the side wall of the muffle 1 however, asshown in FIG. 1, a trolley 6 is preferably used owing to the fact thatthe heating means and the means ensuring the circulation of the hotgases leave the medial portion of the internal volume defined by themuffle l altogether free, thus facilitating and accelerating thecharging and discharging operations.

The general system of circulation of the hot gases within the muffle isas shown by the arrows F in FIG. 1 and results from the trapezoidalshape of the cross-sections of the inner walls of the muffle, normal tothe medial plane 10 in which are placed the fans 2 and 3, in combinationwith the use of deflecting means which, in this case, are constituted bythe casing 5 itself as well as the dihedral rounded angles of the innerrear corners 11a and 11b of the muffle l, axial passageways such as 12and 13 being provided through the casing 5 in alignment with the fans 2and 3.

FIG. 3 is a detailed view of the structure of the casing 5 surroundingthe gas-tube burner 4 so as to protect the latter from the hot gas flowproceeding from the treatment chamber 9 or conveyed thereto the saidcasing is constituted by two vertical and parallel metal sheets 14 andwhich are substantially perpendicular to the axes of the fans 2 and 3the side edges such as 15a of the metal sheet 15 are bent towards thefront, and so are the side edges such as 14a of the metal sheet 14 theedges such as 14a and 15a are sealingly joined together, as by welding,so as to close as completely as possible the inner space of the casing 5for the same reason, the communication between the said inner space andthe general volume of the muffle at the passageways l2 and 13 ispractically completely prevented by means of cylindrical metal sheets12a and 13a connected at their ends to the sheets 14 and 15 the metalsheets 12a and 13a are provided at least at their upper portion withopenings 16, the dimensions of which may be adjustable on the otherhand, the diameter of the metal sheets 12a or 13a is slightly greaterthan that of the fan, the said diameter being for instance on the orderof 10 to 13 cm depending on the size of the oven the opening 16 may beclosed if for instance a malodorous combustive material such as fuel isused according to a modified form of embodiment, no passageway isprovided between the casing 5 and the general volume of the muffle(sealed casing).

The metal sheet 14 of the casing 5 is also provided on its outer surfacewith substantially horizontal ribs or fins 17 serving to improve heatexchange and favor the transverse flow of hot gases in the space 18located between the casing 5 and the rear wall 1c of the muffle.

As seen in FIG. 2, the lower end of the casing 5 is connected to thesole or bed 1b whereas its upper end is connected to the muffle vault 1dthus, the combustion gases may escape through the chimney 18 opening at18a into the upper medial portion of the rear wall 10 of the muffle, ashort metal sheath being provided to connect the opening 18a with anopening 18b located opposite the opening 8a in the rear metal sheet 14of the casing 5.

Thus, the only communication between the general volume of the muffleand the inner space of the casing 5 is through the orifices 16.

The operation of the heat treatment device just described is obvious;the heating takes place in a particularly efficient and uniform manner.Indeed, in addition to the advantages resulting from the use of themeans already described in French patent No. 1,515,884 and its twocertificates of addition, respectively No. 92,009 and No. 92,659, in thename of the Applicant, as regards the system of hot gas circulation inthe treatement chamber, the present device provides the followingimprovements as compared with the already known types of gas ovens therequired temperature within the treatment chamber 9 is attained morerapidly owing to the fact that a greater proportion of the sensible heatof the combustion gases than in the known gas ovens is transferreddirectly to the gases which are made to circulate in the chamber 9 bythe fans 2 and 3, owing, on the one hand, to the fact that the heat ofthe flames is not stored in a heat insulator which subsequently restoresit to the circulating gases and, on the other hand, to the fact that thecombustion gases conveyed to the chimney are not as hot as in the knowndevices owing to the remoteness of the chimney with respect to the gastube burner and owing to the particular position of the lower orifice ofthe chimney which is not located in the muffle vault (braking effect atexit) 1 thermal efficiency is improved, for as already stated, a greaterproportion of combustion heat is transferred to the gases circulating inthe treatment chamber 9, as a result, mainly, of the good heatconductivity of the large metal surface developed by the metal sheets 14and 15 of the casing 5, between the region where heat is produced at theburner 4 and the region where the fumes or burnt gases are eliminated atthe opening 18a moreover, heat exchange is still more improved owing tothe ribs 17, an additional function of which is, as already mentioned,to facilitate the transverse flow of the gases conveyed to the treatmentchamber 9 the cold primary air sucked at the inlet of the ducts 7 and 8is pre-heated owing to a sufficiently long path within the muffle 1,whereas a direct supply of cold air at the gas tube burner 4 wouldresult in the absorbtion of a non-negligible fraction of the heatproduced at the lower portion of the casing 5.

The orifices such as 16 ensure direct passage into the circulating hotgases blown back into the chamber 9 by the fans 2 and 3 of a portion ofthe burnt gases produced in the casing 5, thus imparting moreflexibility to the heating means in operation without prejudicing thestability of the flames.

The heat treatment device shown in FIGS. 4 and 5 comprises a muffle 20and at least one fan 21 secured to the vault 20a of the muffle andlocated in the medial plane 25 thereof, opposite an opening 22 providedin an inner wall 23 of the muffle, defining a treatment chamber 24 inthe general volume of the muffle, the said inner wall 23 beingpreferably constituted by a metal sheet which is for instance suspendedby suitable means from the oven vault 20a (in the case considered, thenumber of fans used depends upon the depth of the muffle, measured fromits front wall provided with the access door to its rear wall).

The heating means are constituted by two gas-tube burners 26a and 26b,each surrounded by a casing 27a or 27b constituted by an invagination ofthe metal sheet 23, the said invagination being open at the level of theflames of the gas burner tubes, so that the combustion gases areconveyed back into the general circulation system of the gases in thetreatment chamber the flames are protected from the direct effect of theflow owing to the end portions such as 27'a, the combustible gas beinginjected at the rear end of the gas burner tubes by an injector 30supported by an arm or bracket 300, which allows auxiliary atmosphericair to be carried along by the gas. Primary air necessary for thecombustion of the gas is fed from the atmosphere through a sheath 280;one of the sides of the sheath 38 is advantageously constituted, as seenin FIG. 4, by a portion 28 of the casing the supply of air at the levelof the flames of the burner tube takes place through a series oforifices 29. Part of the front door 32a is schematically illustrated inFIG. 5.

It is thus possible to make the gas burner flames emerge in the bakingchamber itself while at the same time protecting the flames and, as aresult of the supply of primary air, ensuring good gas combustion inorder to compensate for the said supply, discharge means such as, forinstance, a chimney or a vent, are provided.

Generally, in the devices according to the present invention, theprimary air supply orifices are at least two in number and arrangedeither in the front portion or in the side portion of the device ofcourse, the said primary air may also be mixed beforehand with the fuel,a secondary air supply being possibly provided at the level of theflames. Although the examples illustrated apply solely to the case wherebar-type or tube-type gas burners are used, it is obvious that othertypes of gas burners such as, for instance, single-jet flame typeburners, may be used, such single-jet flame burners being for instanceconstituted by an airfuel mixture injector at the outlet of which thesaid mixture is inflamed.

What is claimed is:

1. In a gas-fired, forced-air convection heating device for food-stuffs,a muffle having a front wall provided with a door, a rear wall oppositesaid front wall, opposed side walls extending between said front andrear walls and connected thereto, and top and bottom walls extendingbetween and connected to the remaining walls, said muffle having avertical medial plane situated midway between and being parallel to saidside walls, said top and rear walls of said muffle forming a pair ofwalls which with said opposed side walls and said bottom and front wallsdefine an interior treatment chamber which in a plane normal to saidmedial plane is of trapezoidal configuration on each side of said medialplane, at least one fan situated in close proximity to and carried byone of said pair of muffle walls, in said medial plane with the interiorspace of trapezoidal configuration on each side of said medial plane insaid plane normal to the latter having its largest base situated in theregion of said fan, an an inner wall situated adjacent that one of saidpair of walls which carries said fan with the latter situated betweensaid inner wall and said one of said pair of walls, said inner wallbeing formed with an opening in alignment with said fan, and heatingmeans for heating the interior of said muffle, said heating meanscomprising a gas burner and a casing extending at least partly aroundsaid gas burner, forming an extension of said inner wall, and having aheat-exchanging relationship with the interior of said muffle fortransferring heat from said burner to the interior of said muffle forgenerating in the latter hot gases circulated by said fan through saidopening of said inner wall into the space between the latter and saidone of said pair of muffle walls, said casing having elongated sideportions situated adjacent but spaced from said side walls to definewith the latter a pair of elongated gaps through which the hot gasesflow from the space between said inner wall and said one of said pair ofwalls into an interior treating portion of said treatment chambersituated on the side of said inner wall opposite from said fan and inwhich the food-stuffs are located to be treated.

2. The combination of claim 1 and wherein said one of said pair of wallsis said rear wall of said muffle, said inner wall being situated infront of said rear wall and being in the form of a metal sheet, saidcasing including a front metal sheet situated forwardly of said innerwall and having a pair of opposed vertical side edges, said inner wallalso having a pair of opposed vertical side edges respectively fixedwith said ogpiostgdvertictzlill sidce1 e ining wi sa1 edges of saidfront metal sheet, an opposed side walls of said muffle said gapsthrough which the hot gases flow, at least one of said metal sheetshaving a rounded configuration and said casing having a lower interiorregion in which said burner is located, and a chimney connected to anupper portion of said casing and communicating with the interiorthereof, and a circular wall defining an air channel, extending betweenand connected to said inner wall and from metal sheet, the latter beingformed with an opening aligned with said opening of said inner wall sothat said circular wall defines an air channel for flow of air throughthe latter channel toward said fan, so that said channel has a rear endcommunicating with the space between said inner wall and rear wall and afront end communicating with said treating portion of said treatmentchamber.

3. The combination of claim 2 and wherein a supporting means forsupporting food-stuffs is located in said treating portion of saidtreatment chamber and is in the form of a removable trolley.

4. The combination of claim 2 and including a means for supplyingprimary air, the latter means including at least one air duct having anelongated section embedded in one of said side walls and a relativelyshort section extending between said elongated section and said casing,communicating with the interior of the latter in the region of saidburner for supplying primary air to the latter.

5. The combination of claim 2 and wherein said circular wall extendingbetween said front sheet metal wall and said inner wall and definingsaid channel is itself formed with openings providing communicationbetween the interior of said casing and the interior treatment chamber.

6. The combination of claim 2 and wherein said inner wall is provided atits surface which is directed toward said rear wall with a plurality ofelongated horizontal ribs which improve the heat-exchanging relationbetween said casing and the interior of the muffle.

7. The combination of claim 1 and wherein said one of said pair of wallsis said top wall, said casing including a pair of casing portionssituated adjacent the opposed side walls of said muffle and said heatingmeans including a pair of burners respectively situated in said pair ofcasings.

1. In a gas-fired, forced-air convection heating device for food-stuffs,a muffle having a front wall provided with a door, a rear wall oppositesaid front wall, opposed side walls extending between said front andrear walls and connected thereto, and top and bottom walls extendingbetween and connected to the remaining walls, said muffle having avertical medial Plane situated midway between and being parallel to saidside walls, said top and rear walls of said muffle forming a pair ofwalls which with said opposed side walls and said bottom and front wallsdefine an interior treatment chamber which in a plane normal to saidmedial plane is of trapezoidal configuration on each side of said medialplane, at least one fan situated in close proximity to and carried byone of said pair of muffle walls, in said medial plane with the interiorspace of trapezoidal configuration on each side of said medial plane insaid plane normal to the latter having its largest base situated in theregion of said fan, an an inner wall situated adjacent that one of saidpair of walls which carries said fan with the latter situated betweensaid inner wall and said one of said pair of walls, said inner wallbeing formed with an opening in alignment with said fan, and heatingmeans for heating the interior of said muffle, said heating meanscomprising a gas burner and a casing extending at least partly aroundsaid gas burner, forming an extension of said inner wall, and having aheat-exchanging relationship with the interior of said muffle fortransferring heat from said burner to the interior of said muffle forgenerating in the latter hot gases circulated by said fan through saidopening of said inner wall into the space between the latter and saidone of said pair of muffle walls, said casing having elongated sideportions situated adjacent but spaced from said side walls to definewith the latter a pair of elongated gaps through which the hot gasesflow from the space between said inner wall and said one of said pair ofwalls into an interior treating portion of said treatment chambersituated on the side of said inner wall opposite from said fan and inwhich the food-stuffs are located to be treated.
 1. In a gas-fired,forced-air convection heating device for food-stuffs, a muffle having afront wall provided with a door, a rear wall opposite said front wall,opposed side walls extending between said front and rear walls andconnected thereto, and top and bottom walls extending between andconnected to the remaining walls, said muffle having a vertical medialPlane situated midway between and being parallel to said side walls,said top and rear walls of said muffle forming a pair of walls whichwith said opposed side walls and said bottom and front walls define aninterior treatment chamber which in a plane normal to said medial planeis of trapezoidal configuration on each side of said medial plane, atleast one fan situated in close proximity to and carried by one of saidpair of muffle walls, in said medial plane with the interior space oftrapezoidal configuration on each side of said medial plane in saidplane normal to the latter having its largest base situated in theregion of said fan, an an inner wall situated adjacent that one of saidpair of walls which carries said fan with the latter situated betweensaid inner wall and said one of said pair of walls, said inner wallbeing formed with an opening in alignment with said fan, and heatingmeans for heating the interior of said muffle, said heating meanscomprising a gas burner and a casing extending at least partly aroundsaid gas burner, forming an extension of said inner wall, and having aheat-exchanging relationship with the interior of said muffle fortransferring heat from said burner to the interior of said muffle forgenerating in the latter hot gases circulated by said fan through saidopening of said inner wall into the space between the latter and saidone of said pair of muffle walls, said casing having elongated sideportions situated adjacent but spaced from said side walls to definewith the latter a pair of elongated gaps through which the hot gasesflow from the space between said inner wall and said one of said pair ofwalls into an interior treating portion of said treatment chambersituated on the side of said inner wall opposite from said fan and inwhich the food-stuffs are located to be treated.
 2. The combination ofclaim 1 and wherein said one of said pair of walls is said rear wall ofsaid muffle, said inner wall being situated in front of said rear walland being in the form of a metal sheet, said casing including a frontmetal sheet situated forwardly of said inner wall and having a pair ofopposed vertical side edges, said inner wall also having a pair ofopposed vertical side edges respectively fixed with said opposedvertical side edges of said front metal sheet, and defining with saidopposed side walls of said muffle said gaps through which the hot gasesflow, at least one of said metal sheets having a rounded configurationand said casing having a lower interior region in which said burner islocated, and a chimney connected to an upper portion of said casing andcommunicating with the interior thereof, and a circular wall defining anair channel, extending between and connected to said inner wall andfront metal sheet, the latter being formed with an opening aligned withsaid opening of said inner wall so that said circular wall defines anair channel for flow of air through the latter channel toward said fan,so that said channel has a rear end communicating with the space betweensaid inner wall and rear wall and a front end communicating with saidtreating portion of said treatment chamber.
 3. The combination of claim2 and wherein a supporting means for supporting food-stuffs is locatedin said treating portion of said treatment chamber and is in the form ofa removable trolley.
 4. The combination of claim 2 and including a meansfor supplying primary air, the latter means including at least one airduct having an elongated section embedded in one of said side walls anda relatively short section extending between said elongated section andsaid casing, communicating with the interior of the latter in the regionof said burner for supplying primary air to the latter.
 5. Thecombination of claim 2 and wherein said circular wall extending betweensaid front sheet metal wall and said inner wall and defining saidchannel is itself formed with openings providing communication betweenthe interior of said casing and the inteRior treatment chamber.
 6. Thecombination of claim 2 and wherein said inner wall is provided at itssurface which is directed toward said rear wall with a plurality ofelongated horizontal ribs which improve the heat-exchanging relationbetween said casing and the interior of the muffle.